The present invention relates to devices for the separation of mixtures of hot materials such as partially molten metals or molten metal compounds and metal mixtures with slag by passing them through a centrifugal separation chamber in a rotary separator drum, and more particularly to an improved method and apparatus for the continual separation of metal slag mixtures which can be used in a continual operating refining process.
Centifugal apparatus for the separation of materials has been known in the art, shown for example, in German Pat. No. 80041 issued Apr. 18, 1894. The utilization of centrifugal drums for the separation of molten metals and metal slag mixtures is basic in principle and can be effective and advantageous, and while attempts have been made to utilize the centrifugal separation principle in the continuous metal smelting industry, difficulties have been encountered which have prevented it from being successful.
It is essential in a continously operating metallurgical plant that the separating stage which is at the end of the complete process must be completely satisfactory and be capable of continual operation, or the entire process will fail. One of the requirements is that the separation device be completely reliable and sturdy and simple in maintenance and repair and can operate under heavy loads with heavy materials in heat environments, and with corrosive materials.
In the separation stages in a continuous metal recovery process, one of the steps has been to heat the separator so that when centifugal separation was used, the centrifugal drum was heated before it was placed into operation substantially to the operating temperature required and was held at that temperature level during operation. Maintaining external parts at a predetermined temperature, created difficulties in that some of the parts were not particularly adapted to high temperature, and it was difficult to maintain drives and bearings, and further this resulted in the consumption of heat energy and required insulation or the encountering of heat losses.
In other operations, oxidation of the metal or metal compounds had to be avoided, and because of the deleterious effect of exposure to air, attempts were made to produce an inert gas zone or a buffering gas environment to protect the surface of the materials from the harmful influence of the cold or of the oxidizing circulating air. The problems have been increased by the fact that good separation of different heavy constituents often requires that the products be subjected to contact with the wall of the centrifugal vessel over a long period of time and that all materials be carried on the centrifuging wall for a relatively uniform time period.
It is accordingly an object of the invention to provide an improved centrifugal separator which is capable of continuous operation in a metallurgical refining system and which avoids disadvantages of the prior art encountered because of cooling of the material during separation and because of exposure of the materials to air with resultant temperature loss or resultant oxidation.
A feature of the invention is to provide a centrifugal drum which rotates about an axis of rotation and wherein a flame conducting pipe is coaxially arranged within the drum extending from the outlet end to the inlet end and wherein the pipe is provided with openings for the outlet of hot flame gases which are directed in continual contact with the material within the drum in a flow path that insures heating of the material and prevents exposure to air. The flame gases are arranged to sweep over the entire surface of the material located in the vessel.
A further feature of the invention provides that the flame conducting pipe or shell is supported so as to rotate with the centrifugal drum and is provided with an end wall opposite the inlet to the centrifugal drum which provides as a distributing and deflecting device for the material being charged into the drum, and the deflected material all engages the wall at the beginning end and is immediately subjected to the sweeping flame gases for its full travel along the length of the interior drum surface. The charging material is accelerated additionally by its engagement with the end distribution wall, and is uniformly directed onto the outer wall of the rotating drum. This insures longer contact with the separating wall of the drum and prevents charging material from disrupting material already on the wall of the drum and being separated. The distributing wall, being part of the flame shell, is heated so that there is no loss in temperature of the entering material.
A further feature of the invention is arrangement at the outlet end of the drum for channeling the flame gases out of the drum for continuous complete circulation therein. At the discharge end, the drum has a circular baffle which extends radially and performs a dual function of regulating the amount of lighter material which flows out of the drum, and also guides the flames radially inwardly to pass out of the drum. The lighter weight slag material and flames fow out through the same passage without interfering with the fuel supply and burner which are centrally located in a coaxial position. Another advantage of the invention lies in an arrangement wherein a mounting is provided which supports the flame shell within the drum and which also supports the conduits for conducting the separated materials from the drum. The supports are in the form of hollow arms which serve as conduits for the separated heavier material leaving the drum and the hollow arms are constructed so as to also conduct flames emerging from the drum so that the flame gases are in contact with the surface of the heavier separated material as it flows away from the drum. The hollow arms extending radially outwardly are positioned so that centrifugal force carries the separated material away and has a ventilating effect on the hot flame gases aiding in the effective circulation through the drum and away from the drum. This arrangement also continues to protect the heavier separated material maintaining it blanketed with hot flame gases and maintaining its temperature.
Other advantages, objects and features, as well as equivalent methods and structures which are intended to be covered herein, will become more apparent with the teaching of the principles of the invention in connection with the disclosure of the preferred embodiments in the specification, claims and drawing, in which: